You just run around the heroes until you are ready to fight them. Seriously, I have made it my stock in trade to sneak/run through areas swarming with enemies in order to pick up loot and visit the shops. It's quite easy once you get the hang of it. This way I can loot Demonis for example without fighting a single enemy. Land of the Dead is much the same. I won't lie and say I never have to reload because an enemy stack caught me, but mostly it's okay. You can also use a boat in Land of the Dead to go around the coast and look for points of entry.
So don't fret about the level 27 hero. There are stacks I've left behind everywhere for later. For example, Ruin Guy (level 14) was too strong for me in Freedom Isles, but now that I'm level 19 he will be a piece of cake when I go back.
